An electronic device often introduces distortion to the signals it processes. A predistorter circuit can be implemented to pre-process the signals before the signals are fed into the electronic device to compensate for the distortion introduced when the signals pass through the device. One example of such an electronic device is a radio-frequency power amplifier. An ideal power amplifier would be efficient and would have a linear response at all frequency ranges. However, a typical power amplifier is most efficient when operated at or near the saturation point, at which point the power amplifier exhibits non-linearities and memory effects. The design of a power amplifier involves a trade-off between linearity and efficiency. One way to improve a power amplifier's efficiency and its overall linearity is to digitally predistort the input to the power amplifier to compensate for the distortion introduced by the power amplifier.
In predistortion, the input signal is adjusted in anticipation of the distortion to be introduced by the device, so that the output signal from the device is largely free of distortions. Predistortion can be quite beneficial in improving the overall performance of a device. Predistorters are usually digitally implemented, in which case the power amplifier system is referred to as a power amplifier with digital predistortion (PA-DPD) system.
In a PA-DPD system, the predistorter can be located remotely from the power amplifier in a centralized processing node. For example, a central processing node may perform predistortion for radio transmitters at multiple remote locations. Such a design reduces power consumption at the remote locations, takes up less space, and offers deployment flexibility. However, when the centralized predistorter is separate from the power amplifiers, transmitting predistorted signals between these two sub-systems requires a relatively large bandwidth due to bandwidth expansion of the predistorted signal.
Accordingly, there remains a need to reduce bandwidth required for transmitting predistorted data from a centralized processing node where the pre-distorted signal is generated to a transmitting node where the pre-distorted signal is amplified and transmitted.